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Abstract:

Disclosed is an organic-inorganic composite material obtained by
chemically modifying a microorganism-derived ceramic material with an
organic group, and a process for producing the organic-inorganic
composite material. The process is characterized by reacting a
microorganism-derived ceramic material with at least one compound
selected from the group consisting of silane coupling agents represented
by formula (1), silane coupling agents represented by formula (2), and
titanate coupling agents represented by formula (3). The
organic-inorganic complex can be used in applications for immobilized
catalysts and immobilized enzyme catalysts.

Claims:

1-17. (canceled)

18. An organic-inorganic composite material obtained by chemically
modifying a microorganism-derived ceramic material comprising a Fe atom
and a Si atom with an organic group.

19. The organic-inorganic composite material according to claim 18,
wherein the element ratio of iron, silicon, and phosphorus is
66-87:2-27:1-32 by atomic %.

20. The organic-inorganic composite material according to claim 18,
wherein the microorganism-derived ceramic material is a material to which
magnetism has been imparted.

22. The organic-inorganic composite material according to claim 18,
wherein the organic group contains at least one functional group selected
from the group consisting of a carboxyl group, a carboxylic acid ester
group, an amide group, an imido group, a cyano group, an isocyano group,
an aldehyde group, a ketone group, an imino group, an amino group, an
azido group, a nitro group, a hydroxy group, an ether group, an epoxy
group, an isocyanato group, an isothiocyanato group, alkyl groups, aryl
groups, alkenyl groups, alkynyl groups, a thiol group, a sulfide group, a
sulfonic acid group, a sulfonic acid ester group, a sulfoxide group,
heterocyclic rings, halogen atoms, a silicon atom, a titanium atom, an
aluminum atom and a phosphorus atom.

23. The organic-inorganic composite material according to claim 18,
wherein the chemical modification with the organic group is performed by
reacting the microorganism-derived ceramic material with at least one
member selected from the group consisting of silane coupling agents,
titanate coupling agents, aluminate coupling agents, and phosphorus
coupling agents.

24. The organic-inorganic composite material according to claim 18,
wherein the organic group functions as a catalyst.

25. A catalytic-organic-inorganic composite material comprising the
organic-inorganic composite material of claim 18 or 20 and a catalyst
immobilized thereon.

26. The catalytic-organic-inorganic composite material according to claim
25, wherein the catalyst is at least one member selected from the group
consisting of enzymes, organic catalysts, and metal complex catalysts.

27. An organic-inorganic composite material comprising the
organic-inorganic composite material of claim 18 or 20 and a dye
immobilized thereon.

28. An immobilized catalyst comprising the organic-inorganic composite
material of claim 24 or the catalytic-organic-inorganic composite
material of claim 25 as an active ingredient.

29. A process for producing an organic-inorganic composite material,
comprising reacting a microorganism-derived ceramic material comprising a
Fe atom and a Si atom with at least one member selected from the group
consisting of: silane coupling agents represented by formula (1):
Y--R1--Si(R2)n(R3)3-n (1) (wherein Y represents
R4R5N--, R7R8N--R6--NR4--; or Y and R1
(Y--R1) conjointly represent a vinyl group, an alkyl group, a phenyl
group, a 3,4-epoxycyclohexyl group, a halogen atom, a mercapto group, an
isocyanate group, an optionally substituted glycidyl group, a glycidoxy
group, an optionally substituted vinyl group, a methacryloxy group
(CH.sub.2.dbd.C(CH3)COO--), an acryloxy group
(CH.sub.2.dbd.CHCOO--), a ureido group (NH2CONH--), an optionally
substituted methacryl group, an optionally substituted epoxy group, an
optionally substituted phosphonium halide group, an optionally
substituted ammonium halide group, or an optionally substituted acryl
group; R4, R5, R7, R8, R10 and R11
independently represent a hydrogen atom or a C1-6 alkyl group;
R6 and R9 independently represent a C2-6 alkylene group;
R1 is a single bond, an alkylene group, or a phenylene group; or
R1 and Y (Y--R1) conjointly represent a vinyl group; each
R2 independently represents an alkyl group or a phenyl group; each
R3 independently represents a hydroxy group or an alkoxy group; and
n is an integer of 0 to 2); silane coupling agents represented by formula
(2): R.sup.12.sub.3Si--NHmR.sup.13.sub.2-m (2) (wherein each
R12 independently represents an alkyl group, each R13
independently represents an alkyl group or an alkylsilane group, and m is
an integer or 0 to 2); and titanate coupling agents represented by
formula (3): Y--R1--Ti(R2)n(R3)3-n (3)
(wherein Y, R1, R2, R3, and n are as defined above) to
chemically modify the organism-derived ceramic material comprising a Fe
atom and a Si atom with an organic group.

30. A process for producing an organic-inorganic composite material,
comprising further performing a chemical modification by utilizing the
organic group contained in the organic-inorganic composite material
obtained by the process of claim 29.

31. A process for producing a catalytic-organic-inorganic composite
material, comprising immobilizing a catalyst on the organic group
contained in the organic-inorganic composite material obtained by the
process of claim 29.

32. A process for producing an organic-inorganic composite material,
comprising binding a dye to the organic group contained in the
organic-inorganic composite material obtained by the process of claim 29.

Description:

TECHNICAL FIELD

[0001] The present invention relates to an organic-inorganic composite
material and a process for producing the organic-inorganic composite
material.

BACKGROUND ART

[0002] Materials that have a unique shape, size, and composition may have
innovative functions and are therefore important. In particular,
materials of a unique shape, size, and composition that cannot be made
artificially have enormous potential for applications. For example, a
ceramic material produced by a representative iron bacterium, Leptothrix
ochracea, is a sheath-shaped substance with a diameter of about 1 μm
and a length of about 200 μm, and the composition of the components
other than oxygen is known to have a Fe:Si:P ratio of about 80:15:5. It
is also known that the hollow structure of the ceramic material is
composed of amorphous nanoparticles with a diameter of 100 nm or less
(about 10 to 40 nm) (Non-Patent Document 1).

[0003] Ceramic materials produced by iron bacteria, which clog pipes and
cause red water, have been only disposed of as waste. However, ceramic
materials are worthy of greater attention because they are derived from
organisms and thus environmentally friendly, and they mainly consist of
the ubiquitous elements iron and silicon and are thus a continuously
available unutilized resource. Moreover, any attempt to artificially
produce such a unique structure would require a huge amount of time and
effort as well as immense technology and energy. Accordingly, the
development of a novel material by utilizing a ceramic material derived
from nature is highly significant in terms of both of science and
technology.

[0004] As carriers for enzymes, inorganic materials, such as diatomaceous
earth, celite, silica, and glass beads, have been used as is. However,
the use of such an inorganic material as is may have problems such as low
enzyme loading and enzyme activity impairment. Accordingly, as a material
suitable for immobilizing enzymes, the development of an
organic-inorganic composite material having a surface modified with an
organic group has been progressing. For example, modified kaolinite
spherical carriers, modified magnetic nanoparticles, modified gold-silica
composite nanoparticles, etc., are known as such materials.

[0005] Toyonite-200M, a modified kaolinite spherical carrier, is a
material produced by modifying a spherical porous ceramic carrier,
Toyonite, obtained by processing kaolinite, with a silane coupling agent.
Toyonite-200M can be used for immobilizing an enzyme (Patent Literature
(PTL) 1 and Non-patent Literature (NPL) 2).

[0006] Modified magnetic nanoparticles are prepared by applying a silane
coupling agent to maghemite nanoparticles. Immobilization of the modified
magnetic nanoparticles and lipase by a covalent bond is disclosed
(Non-Patent Literature (NPL) 3).

[0007] Modified gold-silica composite nanoparticles are prepared by
self-assembly of silica and gold mediated by a polymeric compound,
subsequent sintering treatment, and coordination of the terminal thiol of
an organic group on the gold surface. Further, an enzyme is immobilized
thereon by a covalent bond with a functional group of the organic group
(Non-Patent Document 4).

[0008] However, the bond density of the organic group of such known
materials is not so high. Accordingly, only about 1 mass %, i.e., a very
small amount, of an enzyme can be immobilized thereon. In addition, such
known materials have other problems such as an insufficient level of
durability of enzyme activity.

[0009] Further, for example, lipase, which is an oil and fat hydrolase,
can catalyze hydrolysis of an ester bond as well as transesterification
and esterification reactions in organic solvents. Further, lipase, which
exhibits excellent properties in kinetic optical resolution of racemic
compounds, can find a wide variety of application in the fields of
organic synthesis and pharmaceuticals. Immobilized lipase comprising
diatomaceous earth, celite, Toyonite, or the like as a carrier has
already been widely used. However, such an immobilized lipase poses
problems such as low enzyme loading, and enzyme activity reduction and
enzyme detachment after repeated use. Overcoming these problems would
enable repeated use for a longer period using a smaller reactor,
resulting in an industrially advantage.

[0015] A main object of the present invention is to provide a novel
organic-inorganic composite material produced by performing an artificial
treatment while maintaining various shape features of a ceramic material,
and a process for producing the organic-inorganic composite material.

Solution to Problem

[0016] In view of the above problem of the prior art, the present
inventors carried out extensive research and found that when a ceramic
material obtained from nature, which has various unique shape features,
is chemically treated, an organic-inorganic composite material produced
by chemical modification with an organic group can be obtained. The
inventors further found that a catalyst, etc., can be immobilized on the
thus obtained organic-inorganic composite material by utilizing an
organic group introduced into the organic-inorganic composite material.
The present invention has been accomplished by conducting further
extensive research based on these findings.

[0017] Thus, the present invention provides the organic-inorganic
composite material, process for producing the organic-inorganic composite
material, and composite material produced using the organic-inorganic
composite material shown in Items 1 to 30 below.

[0018] Item 3. The organic inorganic composite material according to Item
1 or 2, wherein the microorganism-derived ceramic material is a material
to which magnetism has been imparted.

Item 4. The organic inorganic composite material according to any one of
Items 1 to 3, wherein the microorganism is an iron bacterium. Item 5. The
organic inorganic composite material according to any one of Items 1 to
4, wherein the microorganism belongs to the genus Leptothrix,
Gallionella, Sphaerotilus, Clonothrix, Toxothrix, Sideromonas,
Siderocapsa, or Siderococcus. Item 6. The organic inorganic composite
material according to any one of Items 1 to 5, wherein the microorganism
is Leptothrix cholodnii. Item 7. The organic inorganic composite
material according to any one of Items 1 to 6, wherein the microorganism
is Leptothrix cholodnii OUMS1 (NITE BP-860). Item 8. The organic
inorganic composite material according to any one of Items 1 to 7,
wherein the ceramic material is in the shape of a sheath, a spiral, a
bar, a grain, a microtube, a nanotube, a hollow string, a capsule, a
thread-like and sphere-like agglomerate, a string, or a rod. Item 9. The
organic inorganic composite material according to any one of Items 1 to 5
and 8, wherein the microorganism is Leptothrix ochracea. Item 10. The
organic inorganic composite material according to any one of Items 1 to
9, wherein the organic group contains at least one functional group
selected from the group consisting of a carboxyl group, a carboxylic acid
ester group, an amide group, an imido group, a cyano group, an isocyano
group, an aldehyde group, a ketone group, an imino group, an amino group,
an azido group, a nitro group, a hydroxy group, an ether group, an epoxy
group, an isocyanato group, an isothiocyanato group, alkyl groups, aryl
groups, alkenyl groups, alkynyl groups, a thiol group, a sulfide group, a
sulfonic acid group, a sulfonic acid ester group, a sulfoxide group,
heterocyclic rings, halogen atoms, a silicon atom, a titanium atom, and a
phosphorus atom. Item 11. The organic inorganic composite material
according to any one of Items 1 to 10, wherein an oxygen atom bound to
the Fe atom and/or Si atom contained in the ceramic material is bound to
silicon, titanium, aluminum, or phosphorus contained in the organic
group. Item 12. An organic inorganic composite material according to Item
11, wherein at least one atom selected from the group consisting of
silicon, titanium, aluminum, and phosphorus contained in the organic
group is derived from a silane coupling agent, a titanate coupling agent,
an aluminate coupling agent, and a phosphorus coupling agent,
respectively. Item 13. The organic inorganic composite material according
to any one of Items 1 to 12, wherein the chemical modification with the
organic group is performed by reacting the microorganism-derived ceramic
material with at least one member selected from the group consisting of
silane coupling agents, titanate coupling agents, aluminate coupling
agents, and phosphorus coupling agents. Item 14. The organic inorganic
composite material according to Item 12 or 13, wherein the silane
coupling agent is at least one member selected from: compounds
represented by formula (1):

Y--R1--Si(R2)n(R3)3-n (1)

(wherein Y represents R4R5N--,
R7R8N--R6--NR4--, or
R11R10N--R9--R7N--R6--NR4--; or Y and
R1 (Y--R1) conjointly represent a vinyl group, an alkyl group,
a phenyl group, a 3,4-epoxycyclohexyl group, a halogen atom, a mercapto
group, an isocyanate group, an optionally substituted glycidyl group, a
glycidoxy group, an optionally substituted vinyl group, a methacryloxy
group (CH2═C(CH3)COO--), an acryloxy group
(CH2═CHCOO--), a ureido group (NH2CONH--), an optionally
substituted methacryl group, an optionally substituted epoxy group, an
optionally substituted phosphonium halide group, an optionally
substituted ammonium halide group, or an optionally substituted acryl
group; R4, R5, R7, R8, R10 and R11
independently represent a hydrogen atom or a C1-6 alkyl group;
R6 and R9 independently represent a C2-6 alkylene group;
R1 is a single bond, an alkylene group, or a phenylene group; or
R1 and Y (Y--R1) conjointly represent a vinyl group; each
R2 independently represents an alkyl group or a phenyl group; each
R3 independently represents a hydroxy group or an alkoxy group; and
n is an integer of 0 to 2); and

[0019] compounds represented by formula (2):

R123Si--NHmR132-m (2)

(wherein each R12 independently represents an alkyl group, each
R13 independently represents an alkyl group or an alkylsilane group,
and m is an integer of 0 to 2). Item 15. The organic-inorganic composite
material according to any one of Items 12 to 14, wherein the silane
coupling agent is at least one member selected from the group consisting
of 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane,
3-mercaptopropyltrimethoxysilane, 3-chloropropyltriethoxysilane,
3-glycidoxypropyltrimethoxysilane, phenyltrimethoxysilane,
n-octadecyltriethoxysilane, 3-(triethoxysilyl)propyltriphenylphosphonium
bromide, 3-(triethoxysilyl)propylammonium bromide, and
hexamethyldisilazane. Item 16. The organic-inorganic composite material
according to Item 12 or 13, wherein the titanate coupling agent is a
compound represented by formula (3):

Y--R1--Ti(R2)n(R3)3-n (3)

(wherein Y represents R4R5N--,
R7R8N--R6--NR4--, or
R11R10N--R9--R7N--R6--NR4--; or Y and
R1 (Y--R1) conjointly represents a vinyl group, an alkyl group,
a phenyl group, a 3,4-epoxycyclohexyl group, a halogen atom, a mercapto
group, an isocyanate group, an optionally substituted glycidyl group, a
glycidoxy group, an optionally substituted vinyl group, a methacryloxy
group (CH2═C(CH3)COO--), an acryloxy group
(CH2═CHCOO--), a ureido group (NH2CONH--), an optionally
substituted methacryl group, an optionally substituted epoxy group, an
optionally substituted phosphonium halide group, an optionally
substituted ammonium halide group, or an optionally substituted acryl
group; R4, R5, R7, R8, R10, and R11
independently represent a hydrogen atom or a C1-6 alkyl group;
R6 and R9 independently represent a C2-6 alkylene group;
R1 is a single bond, an alkylene group, or a phenylene group; or
R1 and Y (Y--R1) conjointly represent a vinyl group; each
R2 independently represents an alkyl group or a phenyl group; each
R3 independently represents a hydroxy group or an alkoxy group; and
n is an integer of 0 to 2. Item 17. The organic-inorganic composite
material according to Item 12, 13, or 16, wherein the titanate coupling
agent is at least one member selected from the group consisting of
3-aminopropyltriethoxytitanium, 3-methacryloxypropyltrimethoxytitanium,
3-mercaptopropyltrimethoxytitanium, 3-chloropropyltriethoxytitanium,
3-glycidoxypropyltrimethoxytitanium, phenyltrimethoxytitanium, and
n-octadecyltriethoxytitanium. Item 18: The organic-inorganic composite
material according to any one of Items 1 to 17, wherein the organic group
functions as a catalyst. Item 19. A catalytic-organic-inorganic composite
material comprising the organic-inorganic composite material of any one
of Items 1 to 17, and a catalyst immobilized thereon. Item 20. The
catalytic-organic-inorganic composite material according to Item 19,
wherein the catalyst is at least one member selected from the group
consisting of enzymes, organic catalysts, and metal complex catalysts.
Item 21. An organic-inorganic composite material comprising the
organic-inorganic composite material of any one of Items 1 to 17 and a
dye immobilized thereon. Item 22. The organic-inorganic composite
material according to Item 21, wherein the dye is a fluorescent dye. Item
23. The organic-inorganic composite material according to Item 21 or 22,
wherein the dye is a porphyrin dye. Item 24. A process for producing an
organic-inorganic composite material, comprising reacting a
microorganism-derived ceramic material with at least one member selected
from the group consisting of:

[0020] silane coupling agents represented by formula (1):

Y--R1--Si(R2)n(R3)3-n (1)

(wherein Y represents R4R5N--,
R7R8N--R6--NR4--, or
R11R10N--R9--R7N--R6--NR4--; or Y and
R1 (Y--R1) conjointly represent a vinyl group, an alkyl group,
a phenyl group, a 3,4-epoxycyclohexyl group, a halogen atom, a mercapto
group, an isocyanate group, an optionally substituted glycidyl group, a
glycidoxy group, an optionally substituted vinyl group, a methacryloxy
group (CH2═C(CH3)COO--), an acryloxy group
(CH2═CHCOO--), a ureido group (NH2CONH--), an optionally
substituted methacryl group, an optionally substituted epoxy group, an
optionally substituted phosphonium halide group, an optionally
substituted ammonium halide group, or an optionally substituted acryl
group; R4, R5, R7, R8, R10 and R11
independently represent a hydrogen atom or a C1-6 alkyl group;
R6 and R9 independently represent a C2-6 alkylene group;
R1 is a single bond, an alkylene group, or a phenylene group; or
R1 and Y (Y--R1) conjointly represent a vinyl group; each
R2 independently represents an alkyl group or a phenyl group; each
R3 independently represents a hydroxy group or an alkoxy group; and
n is an integer of 0 to 2);

[0021] silane coupling agents represented by formula (2):

R123Si--NHmR132-m (2)

(wherein each R12 independently represents an alkyl group, each
R13 independently represents an alkyl group or an alkylsilane group,
and m is an integer of 0 to 2); and

[0022] titanate coupling agents represented by formula (3):

Y--R1--Ti(R2)n(R3)3-n (3)

(wherein Y, R1, R2, R3, and n are as defined above) to
chemically modify the organism-derived ceramic material with an organic
group. Item 25. A process for producing an organic-inorganic composite
material, comprising further performing a chemical modification by
utilizing the organic group contained in the organic-inorganic composite
material obtained by the process of Item 24. Item 26. A process for
producing a catalytic-organic-inorganic composite material, comprising
immobilizing a catalyst on the organic group contained in the
organic-inorganic composite material obtained by the process of Item 24
or 25. Item 27. The process for producing a catalytic-organic-inorganic
composite material according to item 26, wherein the catalyst is at least
one member selected from the group consisting of enzymes, organic
catalysts, and metal complex catalysts. Item 28. A process for producing
an organic-inorganic composite material, comprising binding a dye to the
organic group contained in the organic-inorganic composite material
obtained by the process of Item 24. Item 29. A process for producing an
organic-inorganic composite material according to item 28, wherein the
dye is a porphyrin dye. Item 30. An immobilized catalyst comprising the
organic-inorganic composite material of Item 18 or the
catalytic-organic-inorganic composite material of Item 19 of 20 as an
active ingredient.

Advantageous Effects of Invention

[0023] According to the present invention, a nature-derived ceramic
material that has various unique shape features is chemically treated to
produce an organic-inorganic composite material by chemical modification
with an organic group. In particular, such a ceramic material is reacted
with a silane coupling agent, etc., that can bind an organic material and
an inorganic material to produce a ceramic material having any of various
organic groups and functional groups introduced on the surface (a
chemically modified ceramic material).

[0024] Further, a catalyst, etc., can be immobilized on the ceramic
material by utilizing various functional groups introduced into the
ceramic material. A chemically modified ceramic material that has a
catalyst, etc., immobilized thereon can exhibit excellent catalytic
properties and the like based on various shape features of the original
ceramic material.

[0025] Further, according to the present invention, the magnetic ceramic
material produced by imparting magnetism to a microorganism-derived
ceramic material can be chemically modified. Because a material having
magnetism imparted thereto is attracted and attaches to magnets, the
chemically modified magnetic ceramic material can be easily collected and
reused. Accordingly, this material can be expected to be used in various
fields where magnetic iron oxide has been used, such as in the ceramics
industry, chemical industry, electronics industry, biotechnology
industry, and field of medicine.

BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 shows an SEM photograph of Gallionella ferruginea-derived
ceramic material in the shape of a spiral obtained in the isolation and
purification of microorganism-derived ceramic material (2).

[0027] FIG. 2 shows an optical microscope image (A) and a scanning
electron microscope (SEM) image (B) of the oxide in the shape of a sheath
obtained after culture of OUMS1 strain in a JOP liquid medium.

[0048] The organic-inorganic composite material of the present invention
is obtained by chemically modifying a microorganism-derived ceramic
material with an organic group. (Hereinafter, the ceramic material
chemically modified with an organic group may be sometimes simply
referred to as "chemically modified ceramic material".)

Microorganism-Derived Ceramic Material

[0049] Ceramic materials are inorganic substances produced by various
bacteria and are known to have a variety of shapes. The ceramic material
as used in the present invention preferably contains a Fe atom and a Si
atom on the surface. In the present invention, the surface of the ceramic
material refers to a portion of the ceramic material that may be in
contact with the exterior. For example, when the ceramic material has a
sheath-like structure, the surface includes the outer and inner surfaces
of the sheath structure. When the surface of the sheath structure has a
net-like structure, the surface further includes the inner surface of the
network structure.

[0050] Examples of microorganisms that produce ceramic materials include
iron bacteria. Habitats for iron bacteria are, for example, rivers,
ponds, the ground, and paddy fields. Iron bacteria produce inorganic
substances (ceramic materials) of various shapes, such as the shape of a
sheath, spiral, bar, and grain.

[0051] Examples of iron bacteria that can be used in the present invention
include microorganisms that belong to the genus Leptothrix, Gallionella,
Sphaerotilus, Clonothrix, Toxothrix, Sideromonas, Siderocapsa, and
Siderococcus (see, for example, edited by Sadao Kojima, Ryuichi Sudo, and
Mitsuo chihara: "Pictoral Book of Environmental Microorganisms",
Kodansha, Ltd., (1995)).

[0052] In the present invention, when ceramic materials of various shapes
produced by various microorganisms have a Fe atom and/or a Si atom on the
surface, such ceramic materials can be modified with an organic group by
binding the organic group to or adsorbing the organic group on an oxygen
atom bound to the Fe atom and/or Si atom.

[0053] For example, Leptothrix ochracea, which is a representative iron
bacterium, is known to produce a sheath-shaped ceramic material. (The
sheath-shaped ceramic material produced by Leptothrix ochracea may be
hereinafter sometimes referred to as "sheath shaped ceramic material" or
"biogenous iron oxide".) The ceramic material produced by Leptothrix
ochracea is a sheath shaped substance with a diameter of about 1 μm
and a length of about 200 μm, and is an oxide that contains, in
addition to iron and oxygen, trace amounts of silicon and phosphorus.
Moreover, the sheath-shaped structure is composed of nanoparticles with a
diameter of 100 nm or less (about 10 to 40 nm). The kinds and ratio of
the components, such as iron, silicon, and phosphorus, contained in
ceramics produced by the same kind of microorganism and phosphorus, may
vary according to the environment of the microorganism.

[0054] The sheath shaped ceramic material produced by Leptothrix ochracea
is present, for example, in a sediment precipitated in a gravity
filtration facility of a water purification plant. The Leptothrix
ochracea-derived ceramic material can be purified by subjecting the
sediment to centrifugation, drying under reduced pressure, etc.

[0055] In addition to Leptothrix ochracea, which produces a sheath-shaped
ceramic material, Gallionella, for example, is known to produce a spiral
ceramic material; Sphaerotilus and Clonothrix are known to produce a
branched tubular or thread-shaped ceramic material; Toxothrix is known to
produce a thread-shaped (harp-shaped, pie-wedge-shaped) ceramic material;
Sideromonas is known to produce a short trunk-like ceramic material;
Siderocapsa is known to produce a capsule-shaped ceramic material; and
Siderococcus is known to produce a spherical ceramic material (see, for
example, edited by Sadao Kojima, Ryuichi Sudo, and Mitsuo Chihara
"Pictoral Book of Environmental Microorganisms", Kodansha, Ltd. (1995)).
These ceramic materials can be isolated, purified and analyzed by the
same methods as those for biogenous iron oxide produced by Leptothrix
ochracea.

[0056] In the present invention, ceramic materials derived from
microorganisms that produce iron oxide having a low-crystalline iron
oxide ferrihydrite structure can be used as microorganism-derived (iron
bacteria-derived) ceramic materials.

[0057] The ferrihydrite as used herein refers to a low-crystalline iron
oxide. Ferrihydrite is called 2-line ferrihydrite, 6-line ferrihydrite,
etc. depending on the number of peaks that appear in the X-ray
diffraction pattern. The composition of 2-line ferrihydrite is considered
to be Fe4(O, OH, H2O), and the composition of 6-line
ferrihydrite is considered to be Fe4.6(O, OH, H2O)12 (R.
A. Eggleton and R. W. Fitzpatrick, "New data and a revised structural
model for ferrihydrite", Clays and Clay Minerals, Vol. 36, No. 2, pages
111 to 124, 1988).

[0058] Although any microorganism that can produce iron oxide having a
ferrihydrite structure may be used, the microorganism is preferably
Leptothrix cholodnii. One example of such a microorganism is a Leptothrix
cholodnii OUMS1 strain isolated from a water purification plant. The
Leptothrix cholodnii OUMS1 strain can produce iron oxide having a
ferrihydrite structure. Mycological and genetic properties of the
Leptothrix cholodnii OUMS1 strain are shown below.

(i) Mycological Properties

[0059] The Leptothrix cholodnii OUMS1 strain is a bacillus with a length
of several micrometers and a width of about 1 μm. At the single-cell
stage, this strain actively moves using a flagellum. As the cell grows,
both ends of the cell are connected, and a fibrous material comprising a
polysaccharide and a protein is formed around the cell. As a result, this
cell cannot be uniformly present in a liquid medium and is in an
aggregated and precipitated state. When iron and manganese are added to
the medium, iron oxide and manganese oxide adhere to the fibrous material
that is present outside of the cell, thus forming a sheath-shaped
structure. The cell forms a white amorphous fibrous colony on an agar
medium. When iron is added, the colony becomes yellowish brown. When
manganese is added, the colony becomes brown.

(ii) Genetic Properties

[0060] The nucleotide sequence of 16S rDNA of the Leptothrix cholodnii
OUMS1 strain is shown in SEQ ID NO: 1 of the Sequence Listing. A BLAST
search was performed on the DDBJ database for the nucleotide sequence of
16S rDNA. The results of this search and the mycological properties
described above confirmed that this cell belongs to Leptothrix cholodnii.

[0061] The Leptothrix cholodnii OUMS1 strain was deposited as Accession
No. NITE P-860 in the National Institute of Technology and Evaluation,
Patent Microorganisms Depositary (Kazusa Kamatari 2-5-8, Kisarazu, Chiba,
292-0818, Japan) on Dec. 25, 2009. This bacterial strain has been
transferred to an international deposit under Accession No. NITE BP-860.

[0062] In addition to the Leptothrix cholodnii OUMS1 strain, other
examples of Leptothrix cholodnii that can produce iron oxide having a
ferrihydrite structure include Leptothrix cholodnii having 16S rDNA
consisting of the nucleotide sequence shown in SEQ ID NO: 1. Specific
examples of microorganisms that can produce iron oxide having a
ferrihydrite structure include microorganisms having 16S rDNA consisting
of the nucleotide sequence shown in SEQ ID NO: 1.

[0063] The ceramic material derived from Leptothrix cholodnii or
microorganisms that can produce iron oxide may be in the shape of a
microtube, a nanotube, a hollow string, a capsule, a string-like and
sphere-like agglomerate, a string, a rod, or the like.

[0064] The microorganism-derived ceramic material containing an iron atom
is known to have various structures as described above. The size of the
microorganism-derived ceramic material containing an iron atom as used
herein may vary depending on the kind of material, and is typically about
0.1 to 3000 μm.

[0065] More specifically, for example, the ceramic material in the shape
of a sheath, a spiral, a branched tube, a thread, or a short trunk
typically has a diameter of about 0.1 to 5 μm and a length of about 5
to 3000 μm. The capsule-shaped ceramic material typically has a length
of about 1.2 to 24 μm. The spherical ceramic material has a diameter
of about 0.1 to 1 μm. The microtubular ceramic material has a diameter
of about 0.3 to 4 μm, and a length of about 5 to 200 μm. The
nanotubular ceramic material has a diameter of about 300 to 450 nm and a
length of about 5 to 200 μm. The hollow string-shaped ceramic material
has a length of about 3 to 10 μm. The capsule-shaped ceramic material
has a major axis of 1.5 to 7 μm and a minor axis of 0.5 to 3 μm.
The thread-shaped ceramic material has a length of about 0.5 to 5 μm.
The rod-shaped ceramic material has a length of about 5 to 30 μm.

[0067] For example, the microorganism is cultured in an environment where
a transition metal element such as cobalt, nickel, or manganese, a rare
earth element such as neodymium, and the like are present, whereby the
resulting microorganism-derived ceramic material can contain these
elements. When the ceramic material contains these elements, the magnetic
ceramic material of the present invention can have magnetism derived from
substances other than iron. The ceramic material may further contain
light elements, such as sodium, magnesium, and aluminum.

[0068] The ceramic material derived from Leptothrix cholodnii or iron
oxide-producing microorganisms has a ferrihydrite structure and a fibrous
or scaly surface, which are features of this ceramic material.

[0069] The surface refers to an outer surface of the tube. The term
"fibrous" refers to the state of a surface where thread-like materials
are complicatedly tangled with each other. The term "scaly" refers to a
surface that is covered with scaly substances.

[0070] The components include, for example, Fe, O, Si, and P. The iron
oxide typically further includes a carbon atom and a hydrogen atom. It is
usually preferable that the element ratio of iron, silicon, and
phosphorus is approximately 66-87:2-27:1-32 by atomic %. The iron oxide
of the present invention may be an aggregate of ferrihydrite
microparticles with a primary particle diameter of about 3 to 5 nm.

[0071] The organic-inorganic composite material of the present invention
can be obtained by reacting a compound having an organic group in the
molecule with an oxygen atom (for example, a hydroxyl-derived oxygen)
bound to a Fe atom and/or a Si atom present on the surface of a ceramic
material as mentioned above. More specifically, the organic-inorganic
composite material of the present invention is obtained by chemically
modifying at least part of a ceramic material that can be chemically
modified with an organic group (e.g., an oxygen bound to an Fe atom
and/or a Si atom) with an organic group. This chemical modification
results in the formation of an organic-inorganic composite material
wherein an oxygen atom bound to a Fe atom and/or a Si atom contained in
the ceramic material is bound to one of the silicon, titanium, aluminum,
and phosphorus contained in the organic group.

Magnetic Microorganism-Derived Ceramic Material

[0072] Further, in the present invention, the microorganism-derived
ceramic material to which magnetism (the property of attraction to
magnets) has been imparted (hereinafter referred to as "magnetic ceramic
material") may be chemically modified in the same manner as above to
produce an organic-inorganic composite material. A method for imparting
magnetism to a microorganism-derived ceramic material may be, for
example, a method comprising heat-treating a microorganism-derived
ceramic material containing an iron atom.

[0073] The heat-treatment conditions are not particularly limited, insofar
as the iron atom contained in the microorganism-derived ceramic material
is reduced and oxidized to a magnetic iron oxide (for example,
Fe3O4 and γ-Fe2O3). The heat treatment of the
present invention includes heating accompanied by oxidation, heating
accompanied by reduction, and heating not accompanied by oxidation or
reduction. The heat treatment may be carried out, for example, by an
oxidation method comprising heating at 700 to 900° C. in the
presence of an oxygen gas (for example, atmospheric air), a hydrogen
reduction method comprising heating at about 400 to 650° C. in the
presence of hydrogen gas, or a method of mixing a starting material
ceramic material with an aqueous alkali solution containing a Fe2+
ion prepared by replacement with N2 gas and heating the resulting
mixture under reflux (see, for example, "S. A. Kahani and M. Jafari, J.
Magn. Magn. Mater., 321 (2009) 1951-1954", etc.).

[0074] A preferable method (heat treatment) for producing the magnetic
ceramic material is, for example, a method comprising the following steps
(1) and (2):

[0075] Another example of a preferable method (heat treatment) for
producing the magnetic ceramic material of the present invention is a
method comprising the following step (3) in addition to the heat
treatment comprising the above steps (1) and (2):

[0077] The heating temperature in step (1) is preferably about 700 to
900° C., more preferably about 750 to about 850° C., and
particularly preferably about 800° C. Further, the heating
treatment in step (1) can be carried out, for example, in an atmosphere
in the presence of oxygen (for example, in atmospheric air). The heating
time is typically about 0.1 to 12 hours, preferably about 1 to 4 hours,
and more preferably about 2 hours.

[0078] The heating temperature in step (2) is preferably about 400 to
650° C., more preferably 450 to 600° C., and particularly
preferably about 550° C. The heating reduction time in step (2) is
typically about 1 to 5 hours, preferably 2 to 4 hours, and more
preferably about 3 hours. Step (2) may be carried out in the presence of
hydrogen gas, and preferably in a mixed gas of hydrogen gas with an inert
gas, such as nitrogen or argon. When such a mixed gas is used, the molar
ratio of the inert gas to hydrogen gas may be typically in the range of
about 0:100 to 99:1, preferably about 75:25 to 97:3, and more preferably
about 97:3. The pressure of the mixed gas may be about 0.1 MPa.

[0079] The heating temperature in step (3) is preferably about 100 to
300° C., more preferably 150 to 250° C., and particularly
preferably about 250° C. The heating time in step (3) is typically
about 0.1 to 12 hours, preferably about 1 to 4 hours, and more preferably
about 2 hours. Step (3) can be carried out in an atmosphere in the
presence of oxygen gas, for example, in atmospheric air.

[0080] The heating step in step (1) may be carried out by heating a
starting microorganism-derived ceramic material as mentioned above by
using an electric furnace or the like. Prior to step (1), the
microorganism-derived ceramic material obtained from nature may be dried.
The drying method is not particularly limited and may be a known method,
such as vacuum drying, drying by heating (about 100° C.), and
lyophilization. The heating reduction step in step (2) may be carried out
by heating the ceramic material obtained in step (1) in the presence of
hydrogen gas in an electric furnace. For example, an electric furnace for
hydrogen reduction may be used to perform the heating step in step (2).
As a commercially available electric furnace for hydrogen reduction, for
example, a tubular furnace produced by Koyo Lindberg Ltd. can be used.

[0081] An electric furnace as used in step (1) or the like can be used as
a heating means in step (3).

[0082] When the magnetic ceramic material of the present invention is
subjected to heat treatment, at least part of the iron atoms contained in
the microorganism-derived ceramic material is converted to a structure
such as Fe3O4 or γ-Fe2O3, which has
ferrimagnetism. In the heating (firing) step in step (1), the
microorganism-derived ceramic material produces α-Fe2O3.
α-Fe2O3 (hematite) does not have magnetism, unlike
γ-Fe2O3 (magnetite) and Fe3O4 (maghemite).
α-Fe2O3 obtained in step (1) is subjected to heating
reduction in step (2) to convert α-Fe2O3 to
Fe3O4. Further, Fe3O4 is subjected to oxidation
treatment in step (3) to convert Fe3O4 to
γ-Fe2O3.

[0083] The heating reduction in step (2) is preferably carried out in a
hydrogen gas atmosphere from which oxygen has been removed. The method
for removing oxygen from a mixed gas containing hydrogen gas may be, for
example, passage through an oxygen removal column. The oxygen removal
column may be a commercially available product. For example, a Large
Oxy-Trap produced by GL Sciences Inc. can be used.

[0084] Water is generated during the heating reduction in the presence of
hydrogen gas in step (2). The heating reduction step is preferably
carried out in an atmosphere from which water has been removed. The
method for removing water from the mixed gas containing hydrogen gas may
be, for example, placing a desiccant (for example, P2O5) before
and after the sample in the heating step (2) to thereby perform a
hydrogen reduction step while passing a hydrogen gas-containing mixed gas
from which water has been removed.

[0085] Removal of a trace amount of oxygen in the hydrogen reduction gas
and water generated by the reduction reaction by using methods as
mentioned above can prevent surface oxidation that would otherwise occur
upon cooling the ceramic material, and can convert iron oxide contained
in the magnetic ceramic material into a single phase of Fe3O4
(according to X-ray diffraction (XRD) analysis; the same applies
hereinafter).

[0086] The magnetic ceramic material of the present invention can be
produced by a method comprising steps (1) and (2), or a method comprising
steps (1) to (3).

[0087] The magnetic ceramic material of the present invention that has
been subjected to the above heat treatment contains iron oxide. The
magnetic ceramic material of the present invention has magnetism because
at least one kind of iron oxide contained therein has magnetism. The kind
of magnetic iron oxide is not particularly limited. Examples of magnetic
iron oxides that can be contained in the magnetic ceramic material of the
present invention include ferrimagnetic iron oxides such as
Fe3O4 and γ-Fe2O3. The magnetic ceramic
material of the present invention preferably contains at least one member
selected from the group consisting of Fe3O4 and
γ-Fe2O3.

[0088] The shape of the magnetic ceramic material of the present invention
is generally similar to the shape of the microorganism-derived ceramic
material used as the starting material. More specifically, the magnetic
ceramic material of the present invention may be in the shape of a
sheath, a spiral, a branched tube, a thread (including a thread aggregate
such as a harp or a pie wedge), a short trunk, a capsule, a sphere, a
microtube, a nanotube, a hollow string, a capsule, a string-like and
sphere-like agglomerate, a string, or a rod. The size of the magnetic
ceramic material of the present invention is typically about 0.1 to 3000
μm.

[0089] More specifically, for example, the ceramic material in the shape
of a sheath, a spiral, a branched tube, a thread, or a short trunk
typically has a diameter of about 0.1 to 5 μm and a length of about 5
to 3000 μm, preferably a diameter of about 0.3 to 3 μm and a length
of about 5 to 1000 μm, and more preferably a diameter of about 0.5 to
2 μm and a length of 5 to 200 μm. The ceramic material in the shape
of a capsule typically has a length of about 1.2 to 24 μm. Further,
the spherical ceramic material has a diameter of about 0.1 to 1 μm.
The microtubular ceramic material has a diameter of about 0.3 to 4 μm
and a length of about 5 to 200 μm. The nanotubular ceramic material
has a diameter of about 300 to 450 nm and a length of about 5 to 200
μm. The ceramic material in the shape of a hollow string has a length
of about 3 to 10 μm. The ceramic material in the shape of a capsule
has a major axis of about 1.5 to 7 μm and a minor axis of about 0.5 to
3 μm. The ceramic material in the form of a string has a length of
about 0.5 to 5 μm. The ceramic material in the shape of a rod has a
length of about 5 to 30 μm.

[0091] In the magnetic ceramic material of the present invention, when the
microorganism-derived ceramic material contains silicon and phosphorus in
addition to an iron atom, the ratio of the components is similar to that
in the microorganism-derived ceramic material used as the starting
material. More specifically, when the magnetic ceramic material of the
present invention contains iron, silicon, and phosphorus, the element
ratio of iron, silicon, and phosphorus by atomic % (at %) is typically
66-87:2-27:1-32, and preferably 70-77:16-27:1-9.

[0092] The components of the magnetic ceramic material of the present
invention vary according to the components of the microorganism-derived
ceramic material used as the starting material. As described above, for
example, when a microorganism that can produce a ceramic material is
cultured in an environment in the presence of a transition metal element,
such as cobalt, nickel, or manganese, a rare earth element, such as
neodymium, and the like, the resulting microorganism-derived ceramic
material can contain a transition metal element and a rare earth element.
The magnetic ceramic material of the present invention containing these
elements can have magnetism derived from substances other than iron. The
ceramic material may further contain a light element, such as sodium,
magnesium, and aluminum.

[0093] When the magnetic ceramic material of the present invention
contains silicon and phosphorus in addition to iron, Fe3O4 and
γ-Fe2O3 contained in the magnetic ceramic material and
silicon and phosphorus in the form of solids are not typically dissolved,
and iron, silicon, and phosphorus are phase-separated from each other.
When the magnetic ceramic material of the present invention contains
silicon and phosphorus, the X-ray diffraction (XRD) pattern of the
magnetic ceramic material shows no clear peaks attributable to silicon or
phosphorus. Thus, silicon and phosphorus are considered to be in the form
of an oxide of an amorphous structure.

[0094] The crystallite size of the magnetic ceramic material of the
present invention is, for example, about 5 to 100 nm.

[0095] Further, when iron oxide contained in the magnetic ceramic material
of the present invention is a single phase of Fe3O4, about 60%
of the iron contained in the magnetic ceramic material is
Fe3O4, and about 40% thereof is paramagnetic Fe2+ and
Fe3+. In contrast, when iron oxide contained in the magnetic ceramic
material of the present invention is a single phase of
γ-Fe2O3, about 70% of the iron contained in the magnetic
ceramic material is γ-Fe2O3, and about 30% thereof is
paramagnetic Fe2+ and Fe3+.

[0096] As described in the Examples below, the composition of the
amorphous phase can be calculated from the results of Mossbauer
spectroscopy and the ratio of iron, silicon, and phosphorus in the
microorganism-derived ceramic material used as the starting material,
assuming that paramagnetic Fe2+ and Fe3+ are Fe components that
constitute the amorphous phase. When the ratio of iron, silicon, and
phosphorus in the composition is Fe:Si:P=66-87:2-27:1-32 as mentioned
above and when iron oxide contained in the magnetic ceramic material of
the present invention is a single phase of Fe3O4, the
composition of the amorphous phase has a Fe:Si:P ratio of approximately
36-66:5-55:2-60. When iron oxide contained in the magnetic ceramic
material of the present invention is a single phase of
γ-Fe2O3, the composition of the amorphous phase has a
Fe:Si:P ratio of approximately 39-69:4-51:2-56.

[0097] When the magnetic ceramic material of the present invention
contains at least one member selected from the group consisting of
Fe3O4 and γ-Fe2O3, the total amount of these
magnetic iron oxides in the magnetic ceramic material is typically about
1 to 50 mass %, preferably about 30 to 50 mass %, and more preferably
about 40 to 50 mass %.

[0098] When the magnetic ceramic material of the present invention
contains Fe3O4, the magnetic ceramic material has a saturation
magnetization of typically about 1 to 50 emu/g, preferably about 30 to 50
emu/g, and more preferably about 40 to 50 emu/g. The magnetic ceramic
material typically has a coercivity of about 0 to 2500 e. Moreover, the
magnetic ceramic material has a residual magnetization of about 0 to 20
emu/g. When iron oxide contained in the magnetic ceramic material of the
present invention is a single phase of Fe3O4, the magnetic
ceramic material typically has a saturation magnetization of about 50
emu/g.

[0099] When iron oxide contained in the magnetic ceramic material of the
present invention contains γ-Fe2O3, the magnetic ceramic
material has a saturation magnetization of typically about 1 to 40 emu/g,
preferably about 25 to 40 emu/g, and more preferably about 30 to 40
emu/g. The magnetic ceramic material typically has a coercivity of about
0 to 600 e. The magnetic ceramic material has a residual magnetization of
about 0 to 20 emu/g. When iron oxide contained in the magnetic ceramic
material of the present invention is a single phase of
γ-Fe2O3, the magnetic ceramic material typically has a
saturation magnetization of about 40 emu/g.

[0100] Pure Fe3O4 and γ-Fe2O3 have a saturation
magnetization of 98 emu/g and 81 emu/g, respectively. Accordingly, when
the magnetic ceramic material of the present invention contains
Fe3O4 or γFe2O3, magnetic iron oxide fine
particles of Fe3O4 or γ-Fe2O3 account for about
1 to 50% of the magnetic ceramic material of the present invention, and
the amorphous phase containing oxides of phosphorus, iron, and silicon
accounts for about 25 to 49% thereof.

Organic Group

[0101] In the present invention, the compound containing an organic group
in the molecule is not particularly limited, insofar as the compound has
an organic group, and a group that can be bound to or adsorbed on an
oxygen atom (for example, a hydroxyl-derived oxygen atom) bound to a Fe
atom and/or a Si present on the surface of the ceramic material.

[0102] Examples of organic groups that can be contained in the compound
include those having the following functional groups: a carboxyl group, a
carboxylic acid ester group, an amide group, an imido group, a cyano
group, an isocyano group, an aldehyde group, a ketone group, an imino
group, an amino group, an azido group, a nitro group, a hydroxy group, an
ether group, an epoxy group, an isocyanato group, an isothiocyanato
group, alkyl groups, aryl groups, alkenyl groups, alkynyl groups, a thiol
group, a sulfide group, a sulfonic acid group, a sulfonic acid ester
group, a sulfoxide group, heterocyclic rings, halogen atoms, a silicon
atom, a titanium atom, and a phosphorus atom.

[0103] In the ceramic material into which an organic group containing such
a functional group has been introduced, a catalyst, etc., can be
immobilized on the organic group to thereby produce a
catalytic-organic-inorganic composite material as described below. The
catalytic-organic-inorganic composite material, which can impart a
catalytic function to the ceramic material surface of various shapes, can
exhibit an excellent catalytic feature according to the structure.

[0104] The ceramic material used in the present invention can be bound to
the compound containing an organic group as mentioned above, for example,
via an oxygen atom (such as a hydroxyl-derived oxygen) bound to a Fe atom
and/or a Si atom contained in the ceramic material and via an atom
contained in the organic group, such as silicon, titanium, phosphorus, or
aluminum. Accordingly, the oxygen atom bound to the Fe atom and/or the Si
atom contained in the ceramic material is bound to one of silicon,
titanium, aluminum, and phosphorus contained in the organic group to form
an organic-inorganic composite material.

[0105] The chemically modified ceramic material containing such a bond can
be obtained, for example, by reacting a ceramic material with a silane
coupling agent, a titanate coupling agent, an aluminate coupling agent, a
phosphorus coupling agent, or the like. More specifically, the ceramic
material is surface-treated with a silane coupling agent or the like to
react the surface of the ceramic material with the silane coupling agent
or the like, thus introducing an organic group contained in the silane
coupling agent or the like into the ceramic material.

[0106] Improvement in adhesion of organic-inorganic interfaces is known as
one of the functions of a silane coupling agent. This is achieved by the
following mechanism. A silane coupling agent is hydrolyzed to silanol,
and the silanol is partially condensed to an oligomer. The oligomer is
adsorbed on the inorganic surface by hydrogen bonding and dried, whereby
a hydroxyl group is subjected to a dehydration-condensation reaction to
form a chemical bond, which firmly bonds an inorganic material and an
organic material.

[0107] Silane coupling agents are known to have numerous kinds of organic
groups and functional groups. Accordingly, such silane coupling agents
are particularly excellent as reagents for introducing an organic group
into the ceramic material. In the present invention, known silane
coupling agents can be used. Commercial products are readily available.
Examples of preferable silane coupling agents include compounds
represented by the following general formula (1):

Y--R1--Si(R2)n(R3)3-n (1)

[0108] In formula (1), Y represents R4R5N--,
R7R8N--R6--NR4--, or
R11R10N--R9--R7N--R6--NR4--, or Y and
R1 (Y--R1) conjointly represent a vinyl group, an alkyl group
(preferably a C1-6 alkyl group), a phenyl group, a
3,4-epoxycyclohexyl group, a halogen atom, a mercapto group, an
isocyanate group, an optionally substituted glycidyl group, a glycidoxy
group, an optionally substituted vinyl group, a methacryloxy group
(CH2═C(CH3)COO--), an acryloxy group
(CH2═CHCOO--), a ureido group (NH2CONH--), an optionally
substituted methacryl group, an optionally substituted epoxy group, an
optionally substituted phosphonium halide group, an optionally
substituted ammonium halide group, or an optionally substituted acryl
group. Examples of the substituents include C1-6 (preferably
C1-3) alkyl groups, halogen atoms (preferably chlorine, fluorine,
and bromine, and more preferably chlorine), a phenyl group, and the like.

[0109] R4, R5, R7, R8, R10, and R11 each
independently represent a hydrogen atom or a O1-6 alkyl group, and
R6 and R9 each independently represent an alkylene group having
2 to 6 carbon atoms.

[0110] In formula (1), R1 represents a single bond, an alkylene group
(preferably a C1-6 alkylene group), or a phenylene group, or R1
and Y (Y--R1) conjointly represent a vinyl group. R1 is
preferably a C2-4 alkylene group, and more preferably
C3H6.

[0111] Each R2 independently represents an alkyl group (preferably a
C1-6 alkyl group) or a phenyl group. R2 is preferably a methyl
group or a phenyl group, and more preferably a methyl group.

[0112] Each R3 independently represents a hydroxy group or an alkoxy
group (preferably a O1-6 alkoxy group). R3 is preferably a
C1-3 alkoxy group (including β-methoxyethoxy), and is more
preferably a methoxy group or an ethoxy group.

[0113] The phosphonium moiety of the optionally substituted phosphonium
halide group is preferably represented by the formula
P+R14R15R16-- (wherein two of R14 to R16
are phenyl groups, and one of them is an alkyl group (preferably a
C1-8 alkyl group); or all of R14 to R16 are phenyl groups
(optionally substituted in the 4-position by fluorine or methyl). The
alkyl group is preferably isopropyl, n-butyl, isobutyl, cyclohexyl, or
n-octyl. The optionally substituted phosphonium halide group is
preferably a triphenylphosphonium bromide group.

[0114] The ammonium moiety of the optionally substituted ammonium halide
group is represented by the formula N+R17R18R19--
(wherein each of R17 to R19 is an alkyl group or an aryl group,
and preferably a C1-8 alkyl group or a phenyl group), and the aryl
group and the phenyl group may be substituted with 1 to 4 atoms or groups
selected from halogen atoms, hydroxy, C1-6 alkyl groups, C1-6
alkoxy groups, cyano, nitro, and amino. Examples of alkyl groups
preferably used include methyl, ethyl, isopropyl, n-butyl, isobutyl,
cyclohexyl, n-octyl, and the like. The optionally substituted ammonium
halide group is preferably an ammonium bromide group.

[0115] n is an integer of 0 to 2, preferably, 0 or 1, and more preferably
0.

[0116] Examples of silane coupling agents represented by formula (1)
include the following compounds: silane coupling agents having a vinyl
functional group such as vinyltrimethoxysilane, vinyltriethoxysilane,
vinyltris(β-methoxyethoxy)silane, and p-styryltrimethoxysilane;
silane coupling agents having a methacryloxy functional group such as
3-methacryloxypropyltrimethoxysilane,
3-methacryloxypropyltriethoxysilane,
3-methacryloxypropylmethyldimethoxysilane, and
3-methacryloxypropylmethyldiethoxysilane; silane coupling agents having
an acryloxy functional group such as 3-acryloxypropyltrimethoxysilane,
3-acryloxypropyltriethoxysilane, 3-acryloxypropylmethyldimethoxysilane,
and 3-acryloxypropylmethyldimethoxysilane;

[0117] Among these, silane coupling agents having an amino group, a
mercapto group, a methacryloxy group, an epoxy group, or a halogen atom
are preferable, when the organic-inorganic composite material of the
present invention is further chemically modified as described below.

[0119] Examples of silane coupling agents further include compounds
represented by the formula (2):

R123Si--NHmR132-m (2)

[0120] In formula (2), each R12 independently represents an alkyl
group (preferably a C1-6 alkyl group). Preferably, R12 is a
C1-6 linear alkyl group, and more preferably a C1-3 linear
alkyl group.

[0121] Each R13 independently represents an alkyl group or an
alkylsilane group (wherein the alkyl moiety in the alkyl group or
alkylsilane group preferably contains 1 to 6 carbon atoms). Ru is
preferably a trialkylsilane group. The alkyl group of the trialkylsilane
group typically contains 1 to 6 carbon atoms, and preferably 1 to 3
carbon atoms.

[0122] In formula (2), m is an integer of 0 to 2, and preferably 1.

[0123] Specific examples of silane coupling agents represented by formula
(2) include hexamethyldisilazane and the like.

[0124] Other examples of usable silane coupling agents, which, however, do
not correspond to compounds represented by formula (1) or (2), include
the following: bis(triethoxysilylpropyl)tetrasulfide
((C2H5O)3SiC3H6S4C3H6Si(OC2H-
5)3) bis(trimethoxysilylpropyl)tetrasulfide
((CH3O)3SiC3H6S4C3H6Si(OCH3)3) 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine
(C2H5O)3SiC3H6N═C(CH3) C4H9),
and 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine
(CH3O)3SiC3H6N═C(CH3) C4H9).

[0125] In the present invention, such silane coupling agents may be used
singly or in a combination of two or more.

[0126] Examples of usable titanate coupling agents include known titanate
coupling agents. Titanate coupling agents are known to contain numerous
kinds of organic groups and thus can be suitably used as reagents for
introducing an organic group into the ceramic material.

[0131] In the present invention, such titanate coupling agents may be used
singly or in a combination of two or more.

[0132] Examples of usable aluminate coupling agents include known
aluminate coupling agents. Aluminate coupling agents are known to contain
numerous kinds of organic groups and thus can be suitably used as
reagents for introducing an organic group into the ceramic material.
Examples of such aluminate coupling agents include acetoalkoxy aluminum
diisopropylate, aluminum diisopropoxy monoethyl acetoacetate, aluminum
trisethyl acetoacetate, aluminum trisacetylacetonate, and the like.

[0133] In the present invention, such aluminate coupling agents can be
used singly or in a combination of two or more.

[0147] The C1-3 alkoxy group may be linear or branched. Examples
thereof include methoxy, ethoxy, propoxy, isopropoxy, and
β-methoxyethoxy.

[0148] The aryl group refers to a monocyclic or polycyclic group
comprising a 5- or 6-membered aromatic hydrocarbon ring. Examples thereof
include phenyl, naphthyl, fluorenyl, anthryl, biphenylyl,
tetrahydronaphthyl, and chromanyl.

[0149] The organic-inorganic composite material of the present invention
can be obtained by reacting a ceramic material as mentioned above with a
compound containing an organic group as mentioned above. For example,
when one of the various coupling agents as mentioned above is used as the
compound having an organic group, an organic-inorganic composite material
of the present invention can be produced by mixing the ceramic material
with such a coupling agent in a suitable solvent.

[0150] Examples of usable solvents include diethyl ether, tetrahydrofuran,
dioxane, and like ethers, acetonitrile, dimethylformamide, dimethyl
sulfoxide, toluene, and the like. The amount of solvent is not
particularly limited and can be suitably selected.

[0151] The reaction temperature may be about -30 to 200° C., and
the reaction time may be suitably selected from the range of about 30
minutes to 200 hours. The chemically modified ceramic material obtained
as a reaction product can be isolated by usual separation means, such as
filtration and centrifugation.

[0152] The loading of the organic group in the organic-inorganic composite
material of the present invention may vary according to the kinds of
ceramic material and organic group-containing compound (e.g., silane
coupling agent) used, reaction conditions, etc. The amount of the organic
group in the organic-inorganic composite material is typically about 1 to
30 wt. %, and preferably 5 to 20 wt. %. In the present invention, the
loading is determined by elemental analysis.

[0153] When the organic-inorganic composite material of the present
invention has a structure such that a phosphonium halide alkylsilyl group
or an ammonium halide alkylsilyl group is bound to an oxygen atom bound
to a Fe atom and/or a Si atom contained in the ceramic material, the
organic-inorganic composite material can be used as a catalyst for the
reaction of synthesizing an alkylene carbonate, such as ethylene
carbonate or propylene carbonate, from carbon dioxide and alkylene oxide,
such as ethylene oxide or propylene oxide (see, for example, Japanese
Unexamined Patent Publication No. 2008-296066). The organic-inorganic
composite material wherein a phosphonium halide alkylsilyl group or an
ammonium halide alkylsilyl group is bound to an oxygen atom bound to a Fe
atom and/or Si atom contained in the ceramic material can be produced by
reacting the ceramic material with phosphonium halide
alkyltrialkoxysilane or ammonium halide alkyltrialkoxysilane, which are
silane coupling agents represented by formula (1). The reaction
temperature for this reaction is typically 0 to 200° C., and
preferably 30 to 150° C. The phosphonium halide moiety and the
ammonium halide moiety correspond to the optionally substituted
phosphonium halide group and the optionally substituted ammonium halide
group mentioned above, respectively. The content of phosphonium halide
alkyltrialkoxysilane or ammonium halide alkyltrialkoxysilane in the
organic-inorganic composite material is typically 1 to 20 wt. %, and
preferably 5 to 20 wt. %.

[0154] In the present invention, after an organic group has been
introduced into the ceramic material using a coupling agent as mentioned
above, etc., the organic-inorganic composite material may be further
chemically modified by utilizing a functional group contained in the
organic group. Such a chemical modification can be performed, for
example, by an amidation reaction by condensation of a carboxylic acid
and an amine; an esterification reaction by condensation of a carboxylic
acid and an alcohol; a nucleophilic addition reaction of an amine, an
alcohol, etc., to epoxide; a nucleophilic substitution reaction of an
amine, an alcohol, a thiol, etc., to an organic halogen compound; a
Michael addition reaction of an amine, thiol, etc., to an
α,β-unsaturated carbonyl group; an imine formation reaction by
dehydration condensation of an amino group and an aldehyde group; a
carbon-carbon bonding formation reaction using an organometallic reagent,
such as Grignard reaction or Wittig reaction; and a metal complex
catalyst carbon-carbon bonding formation reaction, such as Suzuki-Miyaura
coupling reaction or olefin metathesis. Further chemical modification by
such a reaction can also convert the functional group contained in a
silane coupling agent or the like to a desired functional group.

Immobilization of the Catalyst

[0155] In the present invention, a catalyst can be immobilized on an
organic-inorganic composite material by utilizing a functional group
contained in an organic group of the organic-inorganic composite material
of the present invention or a functional group introduced by further
chemical modification as mentioned above. In the present invention, the
material produced by immobilizing a catalyst on the organic-inorganic
composite material may be referred to as "catalytic-organic-inorganic
composite material". When a catalyst is immobilized on the
organic-inorganic composite material of the present invention, the
catalyst is present on at least a part of the surface of the ceramic
material, whereby various catalytic properties can be imparted to the
organic-inorganic composite material according to the shape of the
ceramic material.

[0156] Examples of the catalyst immobilized on the organic-inorganic
composite material of the present invention include enzymes, organic
catalysts, metal complex catalysts, and the like. These catalysts can be
immobilized singly or in a combination of two or more.

[0157] Examples of usable enzymes include known enzymes. Examples of
enzymes that can be preferably used in the present invention include
hydrolases, oxidoreductases, transferases, lyases, isomerases, ligases,
and the like.

[0158] Examples of hydrolases include esterases that hydrolyze an ester;
proteases that hydrolyze a peptide bond, such as lipase, pepsin,
chymotrypsin, carboxypeptidase, thermolysin, cathepsin, peptidase,
aminopeptidase, papain, chymopapain, bromelain, protease, hydroxynitrile
lyase, proteinase, and dipeptidase; glucosidases that hydrolyze a
glucosidic bond of a sugar, such as α-glucosidase,
β-glucosidase, α-glucanase, β-glucanase,
α-galactosidase, β-galactosidase, α-amylase,
β-amylase, cellulase, and pullulanase; phosphatases that hydrolyze a
phosphate bond, such as phosphomonoesterase, phosphodiesterase, and
pyrophosphatase; amidases that hydrolyze an amide group, such as
arginase, urease, and glutaminase; and other hydrolases such as nuclease,
lactonase, collagenase, nitrile hydratase, and hydroxynitrile lyase; and
the like.

[0165] Among these enzymes, lipase, carbonyl reductase, and the like are
preferable in the present invention.

[0166] The source of such enzymes may be of animal, plant, or microbial
origin. Purified enzymes are preferable, but crude products may also be
used.

[0167] The organic-inorganic composite material of the present invention
is particularly excellent as a carrier for enzymes. The enzyme
organic-inorganic composite material having an enzyme immobilized thereon
has a high enzyme loading and can exhibit excellent catalytic functions.
For example, lipase, which is an oil and fat hydrolase, can catalyze an
esterification reaction and a transesterification reaction in organic
solvents as well as hydrolysis of ester bonds. In the present invention,
the enzyme organic-inorganic composite material having an enzyme lipase
immobilized thereon exhibits excellent properties in kinetic optical
resolution of racemic compounds, and thus can find a wide variety of
applications in the organic synthesis field and the field of
pharmaceuticals. When a kinetic optical resolution reaction of a racemic
compound is performed using an immobilized enzyme catalyst comprising a
lipase-immobilized enzyme organic-inorganic composite material, the
reaction temperature is typically 0 to 100° C., and preferably 20
to 60° C.

[0168] The immobilized enzyme catalyst comprising the enzyme
organic-inorganic composite material of the present invention can be
maintained for a long period of time and can maintain enzymatic activity
even after repeated use, thus exhibiting excellent properties.
Accordingly, the expensive enzyme is not disposed of but can be
repeatedly used. Furthermore, because the enzyme does not remain in the
reaction product, it can be used as an industrially advantageous
immobilized enzyme.

[0169] The enzyme can be loaded on the organic-inorganic composite
material of the present invention by a usual immobilization method. For
example, it can be easily done by mixing the organic-inorganic composite
material and an enzyme in a solvent, such as a phosphate buffer.

[0170] The amount of enzyme in the immobilized enzyme catalyst comprising
the enzyme-organic-inorganic composite material of the present invention
may vary according to the enzyme and organic-inorganic complex material
used. The amount of enzyme in the enzyme organic-inorganic composite
material may be typically about 1 to 10 wt. %, and preferably about 3 to
5 wt. %. In the present invention, the amount of enzyme is determined by
the Bradford method.

[0171] When the catalyst in the immobilized catalyst comprising the
catalytic-organic-inorganic composite material of the present invention
is an enzyme, the enzyme and a functional group present in an organic
group of the organic-inorganic composite material are immobilized by a
non-covalent bond (intermolecular interaction), such as a hydrogen bond,
adsorption, or the like. Alternatively, the enzyme may be physically
incorporated and immobilized by a sol-gel process or using calcium
alginate.

[0172] The organic catalyst contains no metal elements and is a catalytic
compound that comprises elements such as carbon, hydrogen, oxygen,
nitrogen, sulfur, phosphorus, fluorine, chlorine, bromine, iodine, and
the like. In the present invention, an organic catalyst can be introduced
by utilizing a functional group present in an organic group of the
organic-inorganic composite material. Alternatively, after a
trialkoxysilyl group, i.e., a part of a silane coupling agent, is bound
to an organic catalyst, the resulting catalyst can be reacted with the
ceramic material to introduce the organic catalyst. Examples of such
organic catalysts include asymmetric organic catalysts, etc.

[0173] Examples of usable metal complex catalysts include known metal
complex catalysts. In the present invention, a metal complex catalyst
(including various organic metal catalysts and metal oxides) can be
immobilized by a non-covalent bond (intermolecular interaction), a
covalent bond, adsorption, a coordinate bond, etc., to a functional group
that is present in an organic group of the organic-inorganic composite
material. For example, when a ceramic material is reacted with a chelate
silane coupling agent, such as
3-[2-(2-aminoethylaminoethylamino)propyl]trimethoxysilane to produce a
chemically modified ceramic material, a transition metal such as Pt, Pd,
Co, or Hg can be coordinated thereon. Alternatively, after a functional
group is introduced into a phosphorus ligand and bound to a functional
group that is present in an organic group of the organic-inorganic
composite material, a transition metal such as Pt, Pd, Ru, and Rh can be
coordinated thereon.

[0176] A turbid liquid containing biogenous iron oxide (a ceramic material
in the shape of a sheath produced by Leptothrix ochracea) was collected
from a water purification plant in Joyo City, Kyoto, placed in a 20-L
tank, and allowed to stand to precipitate the biogenous iron oxide. Then,
10 L of the supernatant was removed by decantation, and 10 L of ion
exchange water was added thereto to produce turbidity. The resulting
product was allowed to stand for one day to precipitate the biogenous
iron oxide. This precipitation procedure was repeated 5 times. The
remaining turbid liquid was placed in a centrifuge tube (size: 800 mL),
and an ultrasonic wave was applied thereto for 5 minutes. Thereafter, the
biogenous iron oxide was precipitated by centrifugation (9,000 rpm, 10
minutes), and the supernatant was removed. This procedure was repeated,
and when no more turbid liquid was left in the tank, the biogenous iron
oxide was placed together in one centrifuge tube while being washed with
ion exchange water. It should be kept in mind not to mix the sand
accumulated at the bottom of the centrifuge tube at this time. After
centrifugation, the supernatant was discarded. Subsequently, ethanol
(about 2 L) was added to the biogenous iron oxide in the centrifuge tube,
and the mixture was transferred to a pear-shaped flask and stirred for 1
hour. The ethanol was distilled off with an evaporator. When the residue
was vacuum-dried, 75 g of the biogenous iron oxide (a reddish brown
powder) was obtained. Elemental analysis resulted in C: 1.87% and N:
0.00%. According to the determination of EDX, the elemental ratio of
Fe:Si:P in the biogenous iron oxide was 73:22:5. Non-Patent Literature 1
discloses other methods for characterizing biogenous iron oxide.

[0177] In a manner similar to above, ceramic materials were isolated from
sludge collected from a gutter at the main building of the Faculty of
Engineering of Okayama University. It was confirmed that the sludge
mainly contained a Gallionella ferruginea-derived ceramic material in the
shape of a spiral. FIG. 1 shows an SEM photograph thereof.

[0178] According to the determination of EDX, the elemental ratio of
Fe:Si:P in the obtained ceramic material was 77:18:5.

[0180] Water was collected from groundwater sediment contained in an iron
bacteria tank in the Joyo City Cultural Center in Joyo City, Kyoto, and
placed in a container. A small amount thereof (e.g., 0.5 to 1 g) was
introduced into a JOP liquid medium (0.076 g of disodium
hydrogenphosphate dodecahydrate, 0.02 g of potassium dihydrogenphosphate
dihydrate, 2.383 g of HEPES, and 0.01 mM of iron sulfate, per liter of
sterile groundwater, the pH being adjusted to 7.0 with an aqueous sodium
hydroxide solution) containing iron chips (purity: 99.9%, about 5 mm
square), and sufficiently suspended. Thereafter, the resulting product
was cultured at 20° C. for 10 days in a shaking incubator (70
rpm). A portion of the sediment that increased during the culture was
collected, transferred to a flask containing a fresh JOP liquid medium
containing iron chips, and subjected to shaking culture for another 10
days under the same conditions. This process was repeated once again. A
small amount of the liquid in the flask was collected and diluted with a
JOP liquid medium to 10-2 to 10-6. Each diluted solution was
separately added dropwise to a respective JOP agar plate medium in a
sterile Petri dish and spread-plated onto each of the media with a
sterile glass rod. When the media were cultured at 20° C. for 7 to
10 days in an incubator, the proliferation of the target bacteria and the
formation of an oxide having a sheath shape were observed.

[0181] After the completion of the culture, the obtained single colony
(strain) was individually picked up with a sterilized toothpick,
inoculated into newly prepared JOP agar plate media, and cultured at
20° C. for 10 days. Colonies then appeared on the media. Among
these colonies, an irregularly shaped colony of a light yellowish brown
color was identified. Observation with a low-power optical microscope
confirmed that the majority of the moiety of a light yellowish brown
color was in the sheath structure. The isolated strain having such
properties was designated as an OUMS1 strain.

[0182] A portion of the identified OUMS1 strain colony was scraped,
transferred to a flask containing a newly prepared JOP liquid medium, and
cultured at 20° C. for 10 days in a shaking incubator (70 rpm).
Thereafter, the increased suspended material was placed on a slide glass
and observed with an optical microscope and a scanning electron
microscope. The formation of an oxide having a sheath shape was confirmed
(FIGS. 2-A and 2-B).

[0183] The OUMS1 strain was cultured on a JOP agar plate at 23° C.
for 10 days. 1 mL of a TE buffer (10 mM Tris/1 mM EDTA) was added to the
plate, and the cells were scraped with a cell scraper (produced by TRP)
and collected into an Eppendorf tube. Thereafter, the cells were
collected by centrifugation at 5,000 g for 10 min. The genomic DNA was
extracted by the CTAB method, and the 16S rDNA region was amplified by
PCR with the following primers.

The amplified fragments were TA-cloned using a TA PCR cloning kit
(BioDynamics Laboratory Inc.), and DNA sequencing was performed by the
dideoxy method (Sanger method). The obtained DNA sequence was equal to
the nucleotide sequence of SEQ ID NO: 1. A homology search was performed
for the nucleotide sequence of 16S ribosomal DNA using BLAST from the
DDBJ.

[0187] The OUMS1 strain was cultured at 20° C. for 4 days in an
MSVP (see, for example, Mulder, E. G., and W. L. van Veen Investigations
on the Sphaerotilus-Leptothrix group. Ant, v. Leeuwhoek 29, 121-153
(1963)) liquid medium, and the proliferated bacterial cells were
collected. Then, the genomic DNA was extracted by the CTAB method, and
genomic DNA analysis was performed in accordance with the random
amplified polymorphic DNA (RAPD) method, so as to make a comparison with
the genomic DNA of a known iron-oxidizing bacteria Leptothrix cholodnii
SP-6 strain. FIG. 4 shows the genomic DNA electrophoretic patterns of the
OUMS1 strain and a known iron-oxidizing bacteria Leptothrix cholodnii
SP-6 strain.

[0188] As shown in FIG. 4, in all six types of primers used, the OUMS1
genomic DNA electrophoretic patterns were different from those of known
SP-6 in terms of the length and the number of the amplified fragments.
This clarifies that the OUMS1 strain differs from SP-6.

[0189] A portion of the OUMS1 strain colonies was scraped, transferred to
a flask containing an MSVP liquid medium (Reference 1) containing
manganese sulfate in place of iron sulfate, and cultured at 20° C.
for 10 days in a shaking incubator (70 rpm). Thereafter, the increased
suspended material was placed on a slide glass and observed with an
optical microscope. The formation of an oxide having a sheath shape was
confirmed.

[0190] The OUMS1 strain is the same as a known iron-oxidizing bacteria
Leptothrix cholodnii SP-6 strain in terms of the shape of the culture
colonies, capability of forming a sheath-shaped oxide, and manganese
oxidation capability. Further, because the results of the homology search
for the 16S ribosomal DNA nucleotide sequence confirmed that the OUMS1
strain showed 99% homology with a known iron-oxidizing bacteria
Leptothrix cholodnii SP-6 strain, the OUMS1 strain was identified as
known iron-oxidizing bacteria Leptothrix cholodnii. In addition, because
a comparison of the genomic DNA electrophoretic patterns by the RAPD
method confirmed that the OUMS1 strain differs from a known
iron-oxidizing bacteria Leptothrix cholodnii SP-6 strain, the OUMS1
strain was designated as Leptothrix cholodnii OUMS1 strain (NITE BP-860).

3. Properties of Iron Oxide Formed by OUMS1

[0191] The crystal structure of the iron oxide formed by the OUMS1 strain
was measured using X-ray diffraction (XRD), its composition was analyzed
by energy-dispersive X-ray (EDX) analysis, and the microstructural
observation was evaluated with a scanning electron microscope (SEM) and a
transmission electron microscope (TEM).

[0192] FIGS. 5-A-1 to 5-A-14 as well as 5-B-1 and 5-B-2 show SEM images of
the iron oxide formed by the OUMS1 strain. It was clear that almost all
the structures in sight had a tubular (microtubular) shape on the order
of microns. The outer diameter of the structure was about 1.6 to 3.7
μm, and the internal diameter was about 0.5 to 0.8 μm. The surface
shape of the iron oxide formed by the OUMS1 strain can roughly be
classified into three shapes. Specifically, a surface shape such that
fibrous particles (width of the fiber: about 100 to 200 nm) are sparsely
aggregated as shown in FIGS. 5-A-1 to 5-A-6, a surface shape such that
fibrous particles (the width of the fiber: about 100 to 300 nm) are
densely aggregated as shown in FIGS. 5-A-7 to 5-A-11, and a surface shape
comprising scaly particles as shown in FIGS. 5-A-12 to 5-A-14. In
addition to these, an agglomerate as shown in FIG. 5-B-1, and a
rod-shaped iron oxide having a thickness of about 1 μm shown in FIG.
5-B-2 were also observed.

[0193] FIGS. 6-1 to 6-13 show TEM images of the iron oxide formed by the
OUMS1. In addition to the shapes shown in FIGS. 6-1 to 6-4, which are
similar to the microtubular shapes observed in the SEM images above, the
following shapes were confirmed: a nanotubular shape having an outer
diameter of about 350 to 400 nm as shown in FIGS. 6-5 and 6-6, a hollow
string shape having an outer diameter of about 500 nm and an internal
diameter of about 180 nm as shown in FIG. 6-7, a capsule shape having a
major axis of about 1.5 to 5 μm and a minor axis of about 0.78 to 2.0
μm as shown in FIGS. 6-8 to 6-10, a tubular shape whose one end is
closed, having an outer diameter of about 350 nm and an internal diameter
of about 230 nm as shown in FIGS. 6-11, a shape of a string-like and
sphere-like agglomerate as shown in FIG. 6-12, and a string-like iron
oxide as shown in FIG. 6-13. These results clarified that the OUMS1
formed an iron oxide having various shapes, such as a nanotubular shape,
a hollow string shape, a capsule shape, a shape of a string-like and
sphere-like agglomerate, and a string-like shape, in addition to an iron
oxide in the shape of a microtube.

[0194] As a result of the composition analysis by EDX, it was clear that
the constituent components of the iron oxide formed by the OUMS1 were Fe,
O, Si, and P. Table 1 shows the average values and the standard
deviations of the results of the analysis performed for 24 points. The
composition excluding oxygen was Fe:Si:P=79.3:8.8:11.9. This iron oxide
also contains a carbon atom and a hydrogen atom.

[0195] FIG. 7 shows an XRD pattern of the iron oxide formed by the OUMS1
strain (lowest), and, as comparison samples, XRD patterns of 2-line
ferrihydrite (2nd from the lowest) and 6-line ferrihydrite (3rd from the
lowest). The iron oxide formed by the OUMS1 strain shows peaks that
appear to be a combination of the peaks of 2-line ferrihydrite and 6-line
ferrihydrite. These results clarified that the iron oxide formed by the
OUMS1 was ferrihydrite.

[0196] FIG. 8 shows a high-resolution transmission electron microscope
(HRTEM) image of a typical microtubular iron oxide formed by the OUMS1.
This clarified that the iron oxide formed by the OUMS1 had a primary
particle diameter of about 3 to 5 nm. Further, clear cross stripes were
observed in the primary particles. This clarified that the iron oxide
formed by the OUMS1 was a microcrystal aggregate.

[0197] The results of XRD measurement and HRTEM observation clarified that
the iron oxide formed by the OUMS1 was an aggregate (a ceramic material)
of ferrihydrite nanoparticles, the primary particle diameter thereof
being about 3 to 5 nm.

[0199] The biogenous iron oxide (ceramic material) obtained in the
isolation and purification of ceramic material (1) was dried at
150° C. for 4 hours under reduced pressure using a vacuum pump.
The dried biogenous iron oxide (300 mg) was placed in a reactor, and the
reactor was purged with nitrogen. The silane coupling agent (1.0 mmol)
described in each Example and dry toluene (3 mL) were added thereto,
followed by heating at 100° C. for 24 hours. Then, toluene was
distilled off with an evaporator. Using ethyl acetate, the modified
biogenous iron oxide was transferred to a centrifuge tube, and
centrifugation was performed at 9,000 rpm for 10 minutes. Thereafter, the
supernatant was removed. After this purification procedure was repeated 5
times, the precipitate of the modified biogenous iron oxide was
vacuum-dried. The organic group loading was calculated by elemental
analysis. It is notable that when solid-state NMR, such as 13C
CP/MAS NMR or 29Si CP/MAS NMR, is measured, no NMR signals are
observed, because the presence of paramagnetic iron makes the relaxation
time very short. For this reason, the chemical modification can only be
confirmed by elemental analysis and an infrared absorption spectrum, as
well as, in particular cases, by an ultraviolet-visible absorption
spectrum, a microscope observation, and an evaluation of catalyst
activity expressed by a supporting catalyst.

Example 1

[0200] Chemical Modification of the Biogenous Iron Oxide Using
3-aminopropyltriethoxysilane

[0201] In accordance with the above-described general procedure, the
biogenous iron oxide was chemically modified using
3-aminopropyltriethoxysilane, as shown in the following formula.

##STR00001##

[0202] The formula above is schematically illustrated. In the formula, the
oxygen binding to the biogenous iron oxide and the silicon of the silane
coupling agent may be linked by a triple, double, or single bond, or a
combination thereof. In addition, one or more groups that are introduced
by the chemical modification are present. The same applies to the
following formulae.

[0203] Elemental analysis of the obtained organic-inorganic composite
material resulted in C: 7.85% and N: 1.93%. The organic group loading
calculated from the carbon content was 15.0% (w/w) (1.74 mmol/g).

Example 2

[0204] Chemical Modification of the Biogenous Iron Oxide Using
3-methacryloxypropyltrimethoxysilane

[0205] In accordance with the above-described general procedure, the
biogenous iron oxide was chemically modified using
3-methacryloxypropyltrimethoxysilane, as shown in the following formula.

##STR00002##

[0206] Elemental analysis of the obtained chemically modified biogenous
iron oxide resulted in C: 9.54% and N: 0.10%. The organic group loading
calculated from the carbon content was 14.7% (w/w) (0.94 mmol/g). In
addition, according to the results of FT-IR, C═O stretching vibration
was observed at 1717 cm-1.

[0207] In the process of a series of experimental procedures involving,
for example, attaching an organic group to the biogenous iron oxide and
separating the modified biogenous iron oxide, the characteristic shape
originated from the biogenous iron oxide is not significantly impaired,
apart from the length that is shortened. FIG. 9 shows an SEM photograph
of the obtained modified biogenous iron oxide, and FIG. 10 shows a TEM
photograph thereof. These photographs reveal that the sheath shape of the
biogenous iron oxide and the nanoparticles constituting the sheath-shaped
oxide are maintained even after the process of the chemical modification.

Example 3

[0208] Chemical Modification of the Biogenous Iron Oxide Using
3-mercaptopropyltrimethoxysilane

[0209] In accordance with the above-described general procedure, the
biogenous iron oxide was chemically modified using
3-mercaptopropyltrimethoxysilane, as shown in the following formula.

Further Chemical Modification of the Chemically Modified Biogenous Iron
Oxide Using Organic Group

[0223] In accordance with the following formula, tetraphenylporphyrin was
attached to the amino group present at the surface of the chemically
modified biogenous iron oxide obtained in Example 1.

##STR00009##

[0224] The biogenous iron oxide to which aminopropyl had been introduced
(300 mg), N,N'-dicyclohexylcarbodiimide (DCC) (78.5 mg, 0.380 mmol), and
1-hydroxybenzotriazole (HOBT) (51 mg, 0.377 mmol) were placed in a
reactor, and the reactor was purged with nitrogen. Then, a solution in
which 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin (100 mg, 0.152
mmol) was dissolved in dry tetrahydrofuran (4 mL) was added thereto and
stirred at room temperature for 72 hours. The mixture was subjected to
suction filtration, and washed with tetrahydrofuran, ethanol, heated
ethanol, and hexane in this order, followed by vacuum-drying.

[0226] The ultraviolet-visible absorption spectra confirmed the
introduction of porphyrin to the biogenous iron oxide. FIG. 11 shows
ultraviolet-visible absorption spectra (matrix: barium sulfate) of powder
samples of the porphyrin-modified biogenous iron oxide (red line (upper
line)) and the unmodified biogenous iron oxide (blue line (lower line)).
The Soret absorption band of the porphyrin is clearly observed at 400 to
450 nm, and four Q absorption bands of the porphyrin are clearly observed
at 500 to 650 nm.

[0227] The introduction of porphyrin to the biogenous iron oxide was also
confirmed by observation using an optical microscope. When the biogenous
iron oxide was irradiated with excitation light (530 to 550 nm), a red
fluorescence was emitted by porphyrin (FIG. 12). FIG. 12 is a
bright-field observation image (left) and a fluorescence observation
image (right). The images reveal that porphyrin molecules are attached to
the biogenous iron oxide while being uniformly distributed over the
entire biogenous iron oxide.

[0229] The protein content in the supernatant collected after the
centrifugation and in the aqueous enzyme solution used for immobilization
was quantified by the Bradford method, and the lipase loading was
calculated. The amount of the enzyme carried in the powder (500 mg) was
22.9 mg (4.6% (w/w)).

[0232] The protein content in the supernatant collected after the
centrifugation and in the aqueous enzyme solution used for immobilization
was quantified by the Bradford method, and the lipase loading was
calculated. The amount of the enzyme carried in the powder (501 mg) was
15.3 mg (3.1% (w/w)).

[0279] Comparison was made of the organic group loadings of the untreated
biogenous iron oxide (ceramic material) obtained in the isolation and
purification (1), the chemically modified biogenous iron oxide (ceramic
material) obtained in Example 1, and chemically treated Toyonite 200
(produced by Toyo Denka Kogyo Co., Ltd.) in which a silane coupling agent
was applied as in Example 1. In addition, comparison was made of the
lipase loadings of the chemically modified biogenous iron
oxide-immobilized enzyme obtained in Examples 10 and 11, untreated
biogenous iron oxide and Toyonite 200-immobilized enzyme on which lipase
(BCL or CAL) was immobilized as in Example 10 or 11. Table 2 shows the
results.

[0280] It can be seen from the results that the biogenous iron oxide has a
high loading of both a silane coupling agent and lipase, and that the
biogenous iron oxide can thus be used as an excellent enzyme
immobilization carrier. It can also be seen that when an untreated
biogenous iron oxide is subjected to surface treatment with
3-methacryloxypropyltrimethoxysilane, the lipase loading increases.

[0281] Toyonite 200 is a porous spherical ceramic carrier obtained by
adding a strong acid to a kaolin mineral, subjecting it to hydrothermal
treatment with water, granulating the washed slurry or powder, and firing
the resulting product at 350 to 1,000° C. Toyonite 200 is known as
an excellent inorganic carrier used for lipase immobilization. The
biogenous iron oxide served as a starting material of the
organic-inorganic composite material of the present invention can be
directly obtained from nature. Further, the biogenous iron oxide after
chemical treatment has a higher lipase loading than Toyonite and is thus
very advantageous both economically and environmentally.

[0283] In accordance with the following procedure, the biogenous iron
oxide was chemically modified using
3-(triethoxysilyl)propyltriphenylphosphonium bromide. The biogenous iron
oxide (2.60 g) vacuum-dried at 150° C. for 4 hours was placed in a
reactor, and the reactor was purged with nitrogen. Then, dry toluene (95
mL) was added to the reactor, and
3-(triethoxysilyl)propyltriphenylphosphonium bromide (2.60 g, 4.75 mmol)
dissolved in dimethylformamide (4 mL) was added thereto. The mixture was
stirred at 80° C. for 24 hours. The reaction solution was
transferred to a centrifuge tube while being washed with ethanol. Then,
centrifugation was performed (9,000 rpm, 10 minutes), and the supernatant
was removed. A washing procedure for performing centrifugation with the
addition of ethanol was repeated 4 times. The obtained precipitate was
vacuum-dried.

##STR00016##

[0284] Elemental analysis of the obtained organic-inorganic composite
material resulted in C: 9.40% and N: 0.50%. The organic group loading
calculated from the carbon content was 12.7% (w/w) (0.31 mmol/g).

[0286] The biogenous iron oxide-immobilized organic catalyst obtained in
Example 14 (650 mg, 2 mol %) and 1,2-epoxy hexane (1.20 mL, 10.0 mmol)
were placed in a stainless-steel autoclave. Then, carbon dioxide (1 MPa)
was introduced thereto, and the autoclave was heated at 90° C. for
6 hours. The autoclave was ice-cooled for 30 minutes. The reaction
solution was filtered through Celite to remove the catalyst, and the
resulting product was washed with ether. The obtained solution was
concentrated and vacuum-dried. The crude reaction product was purified by
silica gel-column chromatography, thereby obtaining the target compound
at a 94% yield.

[0289] In accordance with the above-described general procedure, the
biogenous iron oxide (OUMS1 origin) was chemically modified using
3-methacryloxypropyltrimethoxysilane, as shown in the following formula.

[0293] The protein content in the supernatant collected after the
centrifugation and in the aqueous enzyme solution used for immobilization
was quantified by the Bradford method, and the lipase loading was
calculated. The amount of the enzyme carried in the powder (55.6 mg) was
1.5 mg (2.7% (w/w)).

[0298] In accordance with the following procedures (I), (II), and (III),
the ceramic material obtained in isolation and purification (1) was
subjected to heat treatment.

[0299] Procedure (I): A ceramic starting-material dry powder was fired
using an electric muffle furnace OPM-28D produced by Advantech Co., Ltd.,
in atmospheric air at 800° C. for 2 hours. This operation was
performed by rapid heating and quenching.

[0300] Procedure (II): The fired ceramic material obtained by procedure
(I) was subjected to hydrogen reduction at 550° C. for 2 hours in
an electric furnace (a tube furnace produced by Koyo Lindberg Ltd.) in
the presence of H2 (3%)-Ar gas mixture (1 atmospheric pressure).
FIG. 13 schematically illustrates the hydrogen reduction step in
procedure (II). A deoxidation column (a large oxygen trap produced by GL
Sciences Inc.) was disposed immediately in front of H2 (3%)-Ar gas
mixture (0.1 MPa) inlet of the electric furnace, and P2O5 was
placed at the front and back sides of the electric furnace containing the
ceramic starting material to thereby perform the reduction treatment
while removing traces of oxygen in the gas as well as the moisture
generated during the reaction. Before the reduction treatment, the inside
of the furnace was evacuated and then filled with H2 (3%)-Ar gas
mixture. The gas flow rate during the reaction was adjusted to 100 ccm.
The temperature increase rate was 10° C./min, and the cooling was
achieved by quenching.

[0301] Procedure (III): The sample obtained by procedure (II) of Example
18 was heated using an electric muffle furnace OPM-28D produced by
Advantech Co., Ltd., in atmospheric air at 250° C. for 2 hours.
This operation was performed by rapid heating and quenching.

[0303] The XRD patterns of the sample obtained by procedure (I) of Example
18, the sample obtained by procedures (I) to (II) of Example 18, the
sample obtained by procedures (I) to (III) of Example 18, and the ceramic
starting material were measured. FIG. 14 shows the results. For the XRD
measuring device, a RINT-2000 produced by Rigaku Corporation was used. In
the XRD patterns in FIG. 14, the lowest pattern corresponds to the
ceramic starting material, the pattern at the second from the lowest
corresponds to the sample obtained by procedure (I), the pattern at the
third from the lowest corresponds to the sample obtained by procedures
(I) to (II), and the top pattern corresponds to the sample obtained by
procedures (I) to (III).

[0304] FIG. 14 confirmed the following: α-Fe2O3 was formed
almost in a single phase in the sample obtained by procedure (I),
Fe3O4 was formed almost in a single phase in the sample
obtained by procedures (I) to (II), and γ-Fe2O3 was
formed almost in a single phase in the sample obtained by procedures (I)
to (III).

[0305] Additionally, the lattice constants of the sample obtained by
procedures (I) to (II) and the sample obtained by procedures (I) to (III)
were calculated based on the XRD results. The calculated lattice
constants were 8.397 Å and 8.344 Å, respectively. These lattice
constants are in close agreement with the values of pure Fe3O4
and γ-Fe2O3 (8.396 Å and 8.347 Å). This confirmed
that neither Si nor P in the form of solids was dissolved in the
deposited magnetic iron oxide and that Fe, Si, and P were
phase-separated.

[0306] The XRD patterns revealed no clear peaks originating from Si or P.
This suggested that Si and P were forming an oxide having an amorphous
structure. The crystallite size estimated based on the XRD patterns was
confirmed as about 20 nm.

[0307] FIG. 15 shows SEM images of the sample obtained by procedure (I) of
Example 18, the sample obtained by procedures (I) to (II) of Example 18,
the sample obtained by procedures (I) to (III) of Example 18, and the
ceramic starting material. SEM was performed using a Hitachi S-4300
produced by Hitachi, Ltd. FIG. 15 confirmed that the tubular shape of the
ceramic starting material was mostly maintained in the sample obtained by
procedure (I), the sample obtained by procedures (I) to (II), and the
sample obtained by procedures (I) to (III). It was also continued that
almost no difference was found in the surface shape between the sample
obtained by procedures (I) to (II) and the sample obtained by procedures
(I) to (III).

Analysis Example 2

Elemental Analysis

[0308] According to the results of the elemental analysis of the sample
obtained by procedures (I) to (II) of Example 18, the sample had the same
composition ratio as that of the ceramic starting material. Specifically,
for the sample obtained by procedure (II), Fe:Si:P was 73:23:4, and for
the ceramic starting material, Fe:Si:P was 73:22:5. FIG. 16 shows the
elemental mapping results. EDAX Genesis 2000 produced by Ametek, Inc.,
was used for the elemental analysis performed by EDX. Although Fe, Si,
and P were phase-separated, all the elements were uniformly distributed
on the order of submicrons. These results suggest that the phase
separation of Fe, Si, and P occurs on the nano order.

Analysis Example 3

Chemical State Analysis of Iron Based on Mossbauer Spectroscopy

[0309] FIG. 17 shows Mossbauer spectra of the sample obtained by
procedures (I) to (II) of Example 18 and the sample obtained by
procedures (I) to (III) of Example 18. MDF-200 produced by Toyo
Researches (currently Topologic Systems, Inc.) was used for the Mossbauer
spectroscopy measurement. The Mossbauer spectra confirmed that about 60
percent of Fe contained in the sample obtained by procedures (I) to (II)
was Fe3O4, and about 40 percent was paramagnetic Fe2+ and
Fe3+. It was also confirmed that about 70 percent of Fe contained in
the sample obtained by procedures (I) to (III) was
γ-Fe2O3, and about 30 percent was paramagnetic Fe2+
and Fe3+.

[0310] Here, assuming that the paramagnetic Fe2+ and Fe3+
components were the Fe components constituting the amorphous phase, the
composition of the amorphous phase was calculated based on the results of
Mossbauer spectroscopy and composition ratio of the ceramic starting
material, i.e., Fe:Si:P=73:22:5. As a result, the composition of the
amorphous phase of the sample obtained by procedures (I) to (II) of
Example 18 was Fe:Si:P 52:39:9, and the composition of the amorphous
phase of the sample obtained by procedures (I) to (III) was
Fe:Si:P=45:45:10. Table 3 shows the composition of the amorphous phase.

[0311] Using a vibrating sample magnetometer (VSM-5-15, produced by Toei
Industry Co., Ltd.), magnetic properties of the sample obtained by
procedures (I) to (II) of Example 18 and the sample obtained by
procedures (I) to (III) of Example 18 were measured. FIG. 18 and Table 4
show the results.

[0312] The sample obtained by procedures (I) to (II) of Example 18 had a
saturation magnetization of 45 emu/g, a coercivity of 2350e, and a
residual magnetization of 14 emu/g, and the sample obtained by procedures
(I) to (III) had a saturation magnetization of 41 emu/g, a coercivity of
550e, and a residual magnetization of 11 emu/g. It was thereby confirmed
that these samples exhibited ferrimagnetism. The saturation
magnetizations of pure Fe3O4 and γ-Fe2O3 are 98
emu/g and 81 emu/g, respectively. In view of this, it was confirmed that
the sample obtained by procedures (I) to (II) of Example 18 and the
sample obtained by procedures (I) to (III) of Example 18 comprise about
50% of magnetic iron oxide particles, and the other about 50% of an
amorphous phase comprising an oxide of Fe, Si, and P.

[0314] In accordance with the above-described general procedure, the
magnetic ceramic material (γ-Fe2O3) obtained in Example
18 was chemically modified using 3-methacryloxypropyltrimethoxysilane, as
shown in the following formula.

##STR00020##

[0315] Elemental analysis of the obtained chemically modified magnetic
ceramic material (γ-Fe2O3) resulted in C: 3.73% and N:
0.00%. The organic group loading calculated from this carbon content was
6.3% (w/w) (0.41 mmol/g). In addition, according to the results of FT-IR,
C═O stretching vibration was observed at 1717 cm-1. FIG. 19
shows an SEM photograph of the obtained chemically modified magnetic
ceramic material (γ-Fe2O3), and FIG. 20 shows a TEM
photograph thereof. These photographs reveal that the shape of the
magnetic ceramic material is maintained even after the process of the
chemical modification.

[0318] The protein content in the supernatant collected after the
centrifugation and in the aqueous enzyme solution used for immobilization
was quantified by the Bradford method, and the lipase loading was
calculated. The amount of the enzyme carried in the powder (100 mg) was
308 mg (3.8% (w/w)).

[0321] The protein content in the supernatant collected after the
centrifugation and in the aqueous enzyme solution used for immobilization
was quantified by the Bradford method, and the lipase loading was
calculated. The amount of the enzyme carried in the powder (115 mg) was
8.1 mg (7.1% (w/w)).

[0360] In accordance with the above-described general procedure, the
magnetic ceramic material (Fe3O4) was chemically modified using
3-methacryloxypropyltrimethoxysilane, as shown in the following formula.

[0363] The protein content in the supernatant collected after the
centrifugation and in the aqueous enzyme solution used for immobilization
was quantified by the Bradford method, and the lipase loading was
calculated. The amount of the enzyme carried in the powder (102 mg) was
3.3 mg (3.3% (w/w)).

[0370] As shown in the table below, organic-inorganic composite materials
were compared for their performance as an enzyme immobilization carrier.
The organic-inorganic composite materials that were compared were
obtained by chemical modification of the Leptothrix ochracea-derived
ceramic material obtained in the isolation and purification (1), the
magnetic ceramic material (γ-Fe2O3) obtained in Example
18, or maghemite (Toda Kogyo Corp.), using
3-methacryloxypropyltrimethoxysilane. (These are referred to as BIOX-M
(equivalent to the product obtained in Example 2), m-BIOX-M (equivalent
to the product obtained in Example 19), and γ-Fe2O3-M,
respectively.) Secondary alcohols 1a to 1c were reacted under the same
conditions. The TOF values represent an enzyme catalyst turnover
frequency per unit time. BIOX-M shows the most excellent catalyst
activity as a carrier. Compared with the case where BIOX-M was used as a
carrier, the use of m-BIOX-M as a carrier is slightly insufficient in
terms of the catalyst activity, but is excellent in exhibiting magnetism.
Although both are magnetic iron oxides, the use of m-BIOX-M as a carrier
showed much higher catalyst activity, compared with the case where a
synthetic iron oxide (γ-Fe2O3-M) was used as a carrier.
The comparisons above suggest that ceramic materials available in nature
are more appropriate as an immobilization carrier than artificially
synthesized iron oxides.